1. Field of the Invention
The present invention relates generally to a cleaning composition and process for removal of organic, organometallic and metal oxide residues from substrates. More particularly, it relates to such a composition and process for removing semiconductor device fabrication residues from semiconductor device substrates, such as etching residues after plasma etching processes in the fabrication of integrated circuits on silicon wafers and similar processes. Most especially, it relates to such a composition and process which is effective for the removal of these materials while avoiding substantial attack on metal or insulation layers employed in integrated circuits, including titanium layers.
2. Description of the Prior Art
As integrated circuit manufacturing has become more complex and the dimensions of circuit elements fabricated on silicon or other semiconductor wafers have become smaller, continued improvement in techniques used to remove residues formed from such materials has been required. Oxygen plasma oxidation is often used for removal of photoresist or other polymeric materials after their use during the fabrication process has been completed. Such high energy processes typically result in the formation of organometallic and other residues on sidewalls of the structures being formed in the fabrication process.
A variety of metal and other layers are commonly employed in integrated circuit fabrication, including aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal, and the like. The use of such different layers results in the formation of different organometallic residues in the high energy processes. In addition to being effective for removing such residues, cleaning compositions should also not attack the different metallurgies or insulators used in integrated circuit fabrication.
A variety of residue removal compositions and processes suitable for integrated circuit fabrication have been developed and marketed by EKC Technology, Inc., the assignee of the present application. Some of these compositions and processes are also useful for stripping photoresist, polyamide or other polymeric layers from substrates in integrated circuit fabrication, and EKC has also developed a variety of compositions and processes for stripping such polymeric layers from substrates in integrated circuit fabrication. Such compositions and processes are disclosed in the following commonly assigned issued patents: U.S. Pat. No. 5,482,566, issued Jan. 9, 1996 to Lee; U.S. Pat. No. 5,399,464, issued Mar. 21, 1995 to Lee; U.S. Pat. No. 5,381,807, issued Jan. 17, 1995 to Lee; U.S. Pat. No. 5,334,332, issued Aug. 2, 1994 to Lee; U.S. Pat. No. 5,279,771, issued Jan. 18, 1994 to Lee; U.S. Pat. No. 4,824,763, issued Apr. 25, 1989 to Lee and U.S. Pat. No. 4,395,348, issued Jul. 26, 1983 to Lee. These compositions have achieved substantial success in integrated circuit fabrication applications. However, further development of integrated circuits and their fabrication processes have created a need for improvement in residue removal compositions and processes.
As a result of a continuous effort to decrease critical dimension size in the integrated circuit industry, such as in the fabrication of sub-micron size devices, etching residue removal and substrate compatibility with chemicals employed in wet processing is becoming more and more critical for obtaining acceptable yield in very large scale integration (VLSI) and ultra large scale integration (ULSI) processes. The composition of such etching residue is generally made up of the etched substrates, underlying substrate, photoresist and etching gases. The substrate compatibility of the wafers with wet chemicals is highly dependent on the processing of the polysilicon, multilevel interconnection dielectric layers and metallization in thin film deposition, etching and post-etch treatment of the wafers, which are often quite different from one fabrication process to another. Some of the above compositions have produced corrosion on certain metal or insulator substrates, such as those including a titanium metal layer. Titanium has become more widely used in semiconductor manufacturing processes. It is employed both as a barrier layer to prevent electromigration of certain atoms and as an antireflective layer on top of other metals.
Accordingly, it is an object of this invention to provide an improved composition for residue removal and process using such a composition suitable for meeting current semiconductor fabrication requirements.
It is another object of the invention to provide such a composition and process which is suitable for removing residues from wafers and other substrates including one or more titanium metal layers without substantial attack on such titanium layers.
The attainment of these and related objects may be achieved through use of the residue removal composition and process herein disclosed. A residue removal composition in accordance with this invention comprises ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof and water or a polar organic solvent. A process for removing a residue from a substrate in accordance with this invention comprises contacting the substrate with a composition that contains ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof for a time and at a temperature sufficient to remove the residue from the substrate. When the ethylenediaminetetraacetic acid is used in its acid form, it can either be employed alone as the principal active ingredient or in combination with ammonia to form ammonium salt in situ.
In practice, we have found that use of an ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof gives a residue removing composition that attacks titanium, for example, at least about 3 times less than prior compositions. At the same time, the ethylenediaminetetraacetic acid or a mono-, di-, tri- or tetraammonium salt thereof containing composition gives at least equivalent performance as a residue removing composition to prior art cleaning compositions.
The attainment of the foregoing and related objects, advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention, taken together with the drawings, in which: